Immune/inflammatory responses are mediated by a complex series of interactions. One receptor/ligand pair shown to be important in these processes is CD40/gp39. The gp39/CD40 interaction mediates a number of important signaling events between activated T cells and other effector cells of the immune system leading to amplification of an immune/inflammatory response. Responses to signaling through CD40 include T cell help to B cells in the humoral immune response, induction of cytokines by monocytes, and expression of adhesion molecules by endothelial cells.
CD40 is a type I cell surface receptor and a member of the tumor necrosis factor receptor (TNFR) supergene family. Though originally identified as a B cell antigen, CD40 is now believed to be expressed by all antigen presenting cells (APC), including dendritic cells, keratinocytes, and monocytes. CD40 is also expressed by cell types that can act as APC under certain conditions, such as vascular endothelial cells, or cells involved in direct interactions with T cells or T cell precursors such as thymic epithelial cells. More recently, it has also been reported that CD40 can be expressed by fibroblasts, eosinophils, and activated T cells. CD40 expression has also been seen in cancerous cells. Evidence for this is primarily derived from the identification of some carcinoma and melanoma derived cell lines which are CD40.sup.+. (Clark and Ledbetter, Proc. Natl. Acad. Sci. (1986) 83:4494-98; Schriever et al., J. Exp. Med. (1989) 169:2043-58; Caux et al., J. Exp. Med. (1994) 180:1263-72; Alderson et al., J. Exp. Med. (1993) 178:669-74; Young et al., Int. J. Cancer (1989) 43:786-94; Paulie et al., Cancer Immunol. Immunother. (1985) 20:23-28; Denfeld et al., Eur. J. Immunol. (1996) 26:2329-34; Gaspari et al., Eur. J. Immunol. (1996) 26:1371-77; Peguet-Navarro et al., J. Immunol. (1997) 158:144-52; Hollenbaugh et al., J. Exp. Med. (1995) 182:33-40; Galy and Spits, J. Immunol. (1992) 149:775-82; Yellin et al., J. Leukoc. Biol. (1995) 58:209-16; Ohkawara et al., J. Clin. Invest. (1996) 97:1761-66).
This expression pattern differs from the expression pattern of the ligand of CD40, namely gp39. A member of the tumor necrosis factor (TNF) family of proteins, gp39 is a type II cell surface protein that is transiently expressed by activated T cells. Gp39 is also known as CD40L, TRAP, T-BAM, and now has the official CD designation from the Leukocyte Workshop of CD154. In in vitro assays, gp39 appears on the T cells approximately 2-4 hours following T cell activation and levels peak at 6-8 hours. The protein level then rapidly declines and is undetectable 24 hours after stimulation. Gp39 expression has also been detected on eosinophils and mast cells. (Noelle et al., Proc. Natl. Acad. Sci. (1992) 89:6550-54; Hollenbaugh et al., EMBO J. (1992) 11:4313-21; Spriggs et al., J. Exp. Med. (1992) 176:1543-50; Grafet al., Eur. J. Immunol. (1992) 22:3191-94; Covey et al., Mol. Immunol. (1994) 31:471-84; Castle et al., J. Immunol. (1993) 151:1777-88; Roy et al., J. Immunol. (1993) 151:2497-2510; Gauchat et al., Nature (1993) 365:340-43; Gauchat et al., Eur. J. Immunol. (1995) 25:863-65; Koshy et al., J. Clin. Invest. (1996) 98:826-37; Desai-Mehta et al., J. Clin. Invest. (1996) 97:2063-73).
CD40 is a potent signaling receptor, providing a mechanism for activated T-cells to regulate a wide range of immune and inflammatory responses. In vitro and in vivo studies with recombinant forms of the gp39 ligand and with anti-CD40 mAbs have shown that signaling through this receptor leads to a cellular response in all known CD40.sup.+ cells, and that outcome not only varies by cell type but is also modulated by concurrent signaling events through other receptors. In B cells, for example, CD40 signaling in conjunction with signaling by the IL-4 receptor leads to B cell proliferation and production of antibodies of the IgE isotype, while CD40 signaling in conjunction with signals from the IL-10 receptor lead to B cell proliferation and production of antibodies of the IgG isotype (Gordon et al., Eur. J. Inmunol. (1987) 17:1535-38; Rousset et al., J. Exp. Med. (1991) 173:705-710; Jabara et al., J. Exp. Med. (1990) 172:1861-64; Gascan et al., J. Immunol. (1991) 147:8-13). Gp39 mediated CD40 signaling may play a role in cellular immunity through the induction of CD80 and CD86, important T cell costimulatory molecules which bind CD28 and CTLA4 (Goldstein et al., Mol. Immunol. (1996) 33:541-52).
The CD40/gp39 receptor/ligand system is one of the many systems which are involved in the productive interaction between activated T cells and other cells of the immune system. However, a number of findings suggest that this interaction is unique and central to the regulation of the humoral immune response in humans. In particular, defects in gp39 expression or structure have been shown to be the cause of the human immunodeficiency known as X-linked hyper IgM (X-HIM) syndrome. This immunodeficiency is characterized by the inability of affected individuals to produce antibodies other than those of the IgM isotype, indicating that the productive interaction between gp39 and CD40 is required for an effective humoral immune response (Allen et al., Science (1993) 259:990-93; Aruffo et al., Cell (1993) 72:291-300; Di Santo et al., Nature (1993) 361:541-43; Fuleihan, et al., Proc. Natl. Acad. Sci. (1993) 90(6):2170-73; Korthauer et al., Nature (1993) 361:539-541; Notarangelo et al., Immunodef Rev. (1992) 3:101-22). Likewise, recent data indicate that non-X-linked HIM syndrome in humans is caused by defects in the CD40 molecule. Using gene knockout technology, mice lacking CD40 or gp39 have been generated. These mice exhibit a phenotype which has the same characteristics as HIM syndrome suggesting that mice can be an appropriate model in which to test the effects of in vivo treatment with either anti-CD40 or anti-gp39 mAbs that block the interaction between CD40 and gp39 (Kawabe et al., Immunity (1994) 1:167-78; Xu et al., Immunity (1994) 1:423-431; Renshaw et al., J. Exp. Med. (1994) 180:1889-1900; Castigli et al., Proc. Natl. Acad. Sci. USA (1994) 91:12135-39).
The effects of in vivo inhibition of the CD40/gp39 interaction have been extensively studied in normal mice and mouse models of disease using a hamster antimouse gp39 mAb (MR1). The immunosuppressive capacity of the antibody is reflected in its ability to completely inhibit the humoral immune response to T-cell dependent antigens (Foy, et al., J. Exp. Med. (1993) 178:1567-75). Several mouse models of inmmune diseases have also been shown to be inhibited by treatment with the antibody, including those mediated by cellular immune responses. Disease models shown to be inhibited by treatment with anti-gp39 include collagen induced arthritis, experimental allergic encephalomyelitis, lupus nephritis, transplant rejection, and graft vs. host disease (Durie et al., Science (1993) 261:1328-30; Berry, et al., unpublished; Gerritse et al., Proc. Nati. Acad. Sci. USA (1995) 93:2499-504; Mohan et al., J. Immunol. (1995) 154:1470-1480; Larsen et al., Transplantation (1996) 61:4-9; Hancock et al., Proc. Natl. Acad. Sci. USA (1996) 93:13967-72; Parker et al., Proc. Natl. Acad. Sci. USA (1995) 92:9560-64; Durie, et al., J. Clin. Invest. (1994) 94:1333-38; Wallace, et al., unpublished). The role of CD40/gp39 in the amplification of a cellular immune response may be direct, through the stimulation of a subset of activated T cells that are capable of expressing CD40, or indirect, through induction of cytokines and the expression of important co-stimulatory cell surface molecules such as CD80 and CD86, which bind to the T cell receptors CD28 and CTLA-4. The anti-inflammatory effects of the inhibitor have been demonstrated by studies in a mouse model of oxygen-induced lung injury. The effects on inflammation in vivo are suggested by the in vitro results demonstrating stimulation of CD40 on vascular endothelial cells and monocytes which results in the expression of cell adhesion molecules, nitric oxide (NO), matrix metalloproteinases and proinflammatory cytokines (Kiener et al., J. Immunol. (1995) 155:4917-25; Malik et al., J. Immunol. (1995) 156:3952-60; Hollenbaugh et al., J. Exp. Med. (1995) 182:33-40).
Studies with anti-human gp39 mAbs in monkeys have shown that biologics which inhibit the interaction between gp39 and CD40 in vivo are effective immunosuppressive agents in primates. Anti-gp39 mAbs have been demonstrated to be effective in the inhibition of antibody responses to T-cell dependent antigens, and to protect allografts from rejection, results analogous to that seen in rodents.
Collectively the above studies have shown that agents which disrupt the interaction between gp39 and CD40 would be potent immunosuppressive and anti-inflammatory agents. Therefore, there exists a need in the art for an effective method of blocking the CD40/gp39 interaction to provide an immunosuppressive or anti-inflammatory effect. A purpose of the present invention is to provide an antibody which blocks the interaction between gp39 and CD40.
Another object of the present invention is to provide a chimeric antibody effective in blocking the interaction between CD40 and gp39.
An additional object of the present invention is to provide a humanized antibody effective in blocking the interaction between CD40 and gp39.
A further object of the present invention is a method of modulating an immune response by administering an antibody, chimeric antibody, or humanized antibody of the present invention. The method may be useful in treating any number of autoimmune diseases, as well as skin or other organ transplantation.